390, A Bit Smokey...Advice Needed Please

[Diogenes]

I've got a 66 Galaxie Z code 390 (my first FE), which the previous owner went through. He sold me the car at a nice price because it smoked quite a bit and his wife wouldn't ride in it. I got it home, did some homework on this site, and proceeded to check many issues people here have cited as potential problems. I believe it has a high volume oil pump. It has an Edelbrock Performer intake and has C6AE-U heads.

I checked rocker shafts, which were installed correctly. I installed Holley jets to restrict the oil, and installed positive stop valve stem seals on the exhaust side (Comp Cams clamp-on style), and put a new intake gasket on it. All of this reduced the smoke and oil consumption a fair amount, making it drive-able, but it didn't remedy it. Now, after driving it a couple seasons, it's developing again.

When I start the car, it idles well and doesn't smoke until it's been running for a few minutes. I will get in and goose the throttle a few times, and it'll clear up a bit (it only seems to burn on passenger bank). When driving, it seems fine until I come to a stop sign. Sometimes it'll puff a bit pulling up, and them puff off the line--but not always. The car runs very well.

Is there a way to definitively diagnose this problem without pulling the heads? I've been wondering if the heads have been resurfaced a few too many times, causing manifold mating surfaces to be out, but I'm just speculating. I've thought of finding some replacement heads that have been gone through, but I don't want to just throw money at the problem.

Any and all advice would be immensely appreciated.

[machoneman]

What, no compression test results? Leak-down percentages? Vacuum gauge readings? Is the dipstick pushed up after a hard run?
Is a PCV valve present as is it working?

Lots you could tell us......

[Diogenes]

...sorry, looooong day.

No, I don't have any compression or leak-down tests--I've know I need to get to it, but its cold and the garage is too damn small--I guess I need to bite the bullet. The dipstick is not pushed up after a hard run, and I have a PCV that functions properly and is not pulling oil.

The car does run strong.

[cjshaker]

Compression and leak-down tests should be your first course of action at this point. That'll give you a good indicator. Having said that, did you notice any oil fouling in the intake port when you put new intake gaskets in it? If there was a problem with pulling oil from the intake, there should have been signs. Do the plugs show anything, like fouling on certain cylinders, or all? Time to dig in and do some detective work. I feel ya on the cold garage though. Nothing sucks worse than having to work on something with cold or freezing hands.

[C8OZ]

I don't know just how much smoke we're talking about here, but if you haven't ruled out the modulator (if it's an automatic car) it's easy enough to pull the hose off and look for a drip.

[Bolted to Floor]

So...the dipstick pushes out after a hard run. What does that tell us?

[machoneman]

So...the dipstick pushes out after a hard run. What does that tell us?

Lots of crankcase generated blowby from worn, totally shot or stuck piston rings.

[plovett]

So...the dipstick pushes out after a hard run. What does that tell us?

Lots of crankcase generated blowby from worn, totally shot or stuck piston rings.

Beat me to it.  I was going to say it COULD mean blowby.  I am not convinced that is always the case.  I think a long high rpm blast can build crankcase pressure even with good ring seal.  I could be wrong.

Anyway he said it didn't push the dipstick out.

JMO,

paulie

[Drew Pojedinec]

So clean idle cold, smokes when warmed up.

Two thoughts jump into my head.
Stupid rich idle fuel, which a cold engine needs.  When the intake heats up and the fuel finally atomizes it smokes.

Oil thins sufficiently to leak somewhere it shouldn't be.


Things we don't need that we should know:
Ignition, both type, and settings.
Carburetion, same as before?  changed any?

Not saying those are the issues, but they are easy to rule out before tearing into an engine further.

[Heo]

You say you put new valveseals on the exhaust side how about intake side?
Oil drainback from heads? If bad it could flood the valveguides after running
for a while

[Diogenes]

Correct, the dipstick is not pushed out.

Ignition is all stock components, carb is a 750 Holley and it does run pretty rich when cold. The plugs have not been fouled in the past, though I've not looked at them in a little while.

I checked drain back when I first had it apart for intake gasket. The returns seem to be good, but it was flooding the valve covers when I first got the car. Restricting it obviously helped, but I I don't recall what jet size I used to restrict--bigger than 70 if I recall. It also has the tins for drainback.

Yeah, its a C6 car, so I will have a look at the modulator--that is one of the potential issues I never tracked down.

If I remember correctly, the intake did show signs of leakage. My corrective actions when I first got the car remedied a lot of the problem, but it seems to have slowly crept back. The smoking is not horrendous, but I don't want to see any smoke.  My mind keeps returning to the intake leaking (again), though I know I need solid facts, not speculation, so the compression and leak down tests are my next steps (but I'll check the modulator).

The curse of a small, cold garage is soon to be remedied. It's frustrating losing an entire Winter of downtime due to not having a decent working garage, something I've always had up until the last 2 years. Cold and snow season is for working on the car, sunny and dry is for driving it--not so this year--damn it 

Once I get around to getting numbers, I'll post it up--thank you for all the expert advice!

[plovett]

What type of intake manifold gaskets did you put on it?

Felpro Printoseals "printosuck".  I've used them before and in a street car with anti-freeze they tend to fail pretty quickly.

paulie

[plovett]

So just thinking here.  Go ahead and laugh.    Since your smoke occurs more at idle where vacuum is higher, that makes me think it could be vacuum related, which points to the intake gasket.  Maybe?  Or since it runs fine until you get to a stop, maybe the valve stem seals are okay until you have been running it at higher rpm for a bit. The oil accumulates in the cylinder head and then you stop and they suck in oil? 

I was turned on to Viton seals a long time ago by MY427Stang and am a believer now.  They just work.  I think I am echoing what others have already said.  I would look at the intake gaskets if they are Printoseals, and I would consider changing the valve stem seals to viton types.

Of course also do the compression test and especially a leakdown test.  More info is more better.

JMO,

paulie

[fryedaddy]

i had a 390 that smoked and had a intake leak.i took it apart and i used a generous amount of sealer on the gasket and walls and it stopped smoking.  just a thought.

[Diogenes]

What type of intake manifold gaskets did you put on it?

Felpro Printoseals "printosuck".  I've used them before and in a street car with anti-freeze they tend to fail pretty quickly.

paulie

I didn't use the Print-o-sucks, as there were plenty of people warning against them. I used Mr. Gasket.

@plovett, I've been thinking much the same as you, but you're correct, I still need numbers. I'd have to check, but I may have installed viton seals.

@fryedaddy, I did the same when I replaced the gaskets, using sealer, given all the problems I've read with intake gaskets leaking.